The importance of metal sensitivity in morbidity associated with the use of metallic orthopaedic implants will be assessed. Sensitivity to nickel, cobalt, and chromium is being assessed by the use of an LIF test in agarose. Implants being removed from orthopaedic patients undergo metallurgical analysis and these findings are then correlated with the patient's symptoms and the LIF test. Poor quality of the metal alloy is associated with more frequent development of symptoms. The immunologic status of patients reacting to the metallic implant is being assessed. Similar studies are being undertaken in the rabbit and the guinea pig.